This invention relates to communication between circuit-switched and packet-switched networks, and more particularly, to methods and apparatus for switching real-time voice signals between these two types of networks.
Various packet-switched voice communications systems have been developed exclusively for communications within a packet-switched computer network, such as the Internet. These systems include software running on two computers which communicate with each other using a client-server model. A user speaks into a microphone connected to a source computer. The user""s voice is digitized and is placed into data packets by a client process on the source computer. The packets of voice data are then sent over the packet-switched network to a server process on the destination computer. The server process extracts the voice data from the packet, converts it to analog format and sends the analog signal to a speaker. Full-duplex communication is provided by having each computer run both a client process for sending and a server process for receiving. An example of such a software package is Microsoft Corporation""s NetMeeting Software.
One drawback to these types of systems is that communications are strictly limited to other computer users on the packet-switched computer network. Since the voice is digitized and placed into packets which are sent one at a time over the network, only computers which are interconnected to the same network and use the same protocols have the ability to communicate with each other. Packet-switched networks are referred to as connectionless networks, since each individual packet may take a different route through the network on its way from a source to a destination computer. The end user perceives a seamless connection referred to as a virtual circuit.
By contrast, circuit-switched networks, such as the Public Switched Telephone Network (PSTN), use a vast network of interconnected switching centers known as the Public Switched Telephone Network (PSTN). On these networks, special signaling is used to set up a dedicated circuit connection for the duration of a telephone call. Since the same physical circuit is used to send and receive voice signals during the entire call, these networks are referred to as connection oriented networks.
Interconnecting circuit and packet-switched networks presents a problem. Since the two types of networks use different signaling and protocols at various data communications layers, the communication techniques of these networks are incompatible. Wiring that is commonly used for packet-switched networks, such as Ethernet cable, is incompatible with circuit-switched networks, which commonly use twisted pair cabling.
Accordingly, there is a need for a method and apparatus for interconnecting voice connections between circuit-switched and packet-switched networks.
According to a first aspect of the invention, a system for establishing voice communication between a packet-switched network and a circuit-switched network is provided. The system comprises a network interface unit for coupling to the packet-switched network, a phone interface unit for coupling to the circuit-switched network and a gateway processor coupled to the network interface unit and coupled to the phone interface unit. The gateway processor, the network interface unit and the phone interface unit respond to a call request received from a first station in the packet-switched network or a second station in the circuit-switched network by establishing a packet-switched network connection through the network interface unit between the first station and the gateway processor and by establishing a circuit-switched network connection through the phone interface unit between the second station and the gateway processor. Incoming voice data packets received from the first station over the packet-switched network connection are converted to outgoing voice signals that are compatible with the circuit-switched network. The outgoing voice signals are transmitted over the circuit-switched network connection to the second station. Voice signals received from the second station over the circuit-switched network connection are converted to outgoing voice data packets. The outgoing voice data packets are transmitted over the packet-switched network connection to the first station. Thus, two-way voice communication is established between the first station and the second station. The system may be configured to permit origination of a call request from the first station in the packet-switched network, the second station in the circuit-switched network, or both.
The packet-switched network connection may include an incoming packet-switched network connection and an outgoing packet-switched network connection. The circuit-switched network connection may include an incoming circuit-switched network connection and an outgoing circuit-switched connection. The gateway processor may execute a server process for establishing the incoming packet-switched network connection and the outgoing circuit-switched network connection and for controlling reception of the incoming voice data packets from the first station over the incoming packet-switched network connection and transmission of the outgoing voice signals to the second station over the outgoing circuit-switched network connection. The gateway processor may further execute a client process for establishing the incoming circuit-switched network connection and the outgoing packet-switched network connection and for controlling reception of the incoming voice signals from the second station over the incoming circuit-switched network connection and transmission of the outgoing voice data packets to the first station over the outgoing packet-switched network connection. In another embodiment, the server process and the client process are combined in a single process.
The gateway processor may include conference call means responsive to a conference call request received from the first station or the second station for establishing a conference call among three or more conference call participants. At least one of the conference call participants is located in the packet-switched network, and at least one of the conference call participants is located in the circuit-switched network. The conference call means includes means for establishing a conference call network connection to each of the conference call participants.
According to another aspect of the invention, a method for establishing voice communication between a packet-switched network and a circuit-switched network is provided. A gateway computer is interconnected between a packet-switched network and a circuit-switched network. The gateway computer responds to a call request received from a first station in the packet-switched network or a second station in the circuit-switched network by establishing a packet-switched network connection between the first station and the gateway computer, and by establishing a circuit-switched network connection between the second station and the gateway computer. The gateway computer responds to incoming voice data packets received from the first station over the packet-switched network connection by converting the incoming voice data packets to outgoing voice signals that are compatible with the circuit-switched network and by transmitting the outgoing voice signals over the circuit-switched network connection to the second station. The gateway computer responds to incoming voice signals received from the second station over the circuit-switched network connection by converting the incoming voice signals to outgoing voice data packets and by transmitting the outgoing voice data packets over the packet-switched network connection to the first station. Thus, two-way voice communication is established between the first station and the second station.
According to a further aspect of the invention, a method for establishing voice communication between a first station in a first circuit-switched network and a second station in a second circuit-switched network is provided. A first circuit-switched network connection is established between the first station and a first gateway computer. The first gateway computer is interconnected between the first circuit-switched network and a packet-switched network. A packet-switched network connection is established between the first gateway computer and a second gateway computer in the packet-switched network. The second gateway computer is interconnected between the packet-switched network and the second circuit-switched network. A second circuit-switched network connection is established between the second gateway computer and the second station through the second circuit-switched network. Voice information is sent between the first station and the second station over the first circuit-switched network connection, the packet-switched network connection, and the second circuit-switched circuit connection.